Interdisciplinary Monitoring for the Ecosystem of Kuroshio Warm Current Area in Relation to Climate Change

Interdisciplinary monitoring for the ecosystem of Kuroshio warm current area in relation to climate change

Hiroya Sugisaki (Zooplankton, Database, Project organizer), Kiyotaka Hidaka (Zooplankton, Phytoplankton), Tadafumi Ichikawa (Phytoplankton, Nutrient), Yutaka Hiroe (Phisical Oceanography), Yuuichi Hirota (Zooplankton), Kenji Morinaga (Physical Oceanography), Manabu Shimizu (Physical Oceanography, Model), Takahisa Tokunaga (Nutrient), Mikiko Kuriyama (Zooplankton), Tomowo Watanabe (Database, Model), and Kaoru Nakata (Zooplankton, Project Organizer) （NRIFS) KuroshioKuroshio warmwarm currentcurrent areaarea

130oE 135oE 140oE Japan archipelago Joban sea Honshu I. area

Izu pen. Shikoku I. Kii pen. Cape Omaezaki East Enshu‐nada Kuroshio Extension Tosa‐Ｂａｙ Sea area China Kyushu I. Cape Sea Shionomisaki

Kuroshio

Ogasawara Is. 30oN

Tokara strait Tokara strait Width: 100km Depth: >500m Current speed: 2-4knt ImportanceImportance ofof KuroshioKuroshio areaarea forfor pelagicpelagic fishfish productionproduction

Nursery and feeding ground of pelagic fish Kuroshio is very important area for early life stage of sardine and anchovy The Kuroshio Extension

The Kuroshio Tosa Bay warm current Spawning ground of sardine Monitoring line and saury off御前崎沖定線 cape Omaezaki (138(O-LineoE：O-line) ) 中央ブロック since 1999. Long term variation of stock size of the pelagic fishes has Known as low productive area been observed, and it implies that the Kuroshio paradox variation is relating to climate change. Habitat for early life stages of abundant fishery important pelagic fishes

Field monitoring to clarify the mechanism of abundaabundantnt pelagic fish production Larval and juvenile Prey for pelagic fish larval pelagic fish Meso-zooplankton （copepods, appendicularia）

Microzooplankton (ciliates etc.) Large particle food chain phytoplankton （diatoms etc.） Heterotrophic nannoflagellates ("HNF")

Small particle food chain bacteria Low trophic level Picophytoplankton ecosystem (coccoliths etc.)

Trophic cascade from primary production to larval fish in Kuroshio area Typical patterns of the meander of Kuroshio current

Depth (m) Depth

Large meander period

33 ) 32

31 Latitude (N 30

1975 1980 1985 1990 1995 2000 2005 Souuthmost latitude of Kuroshio : large meander period

AnnualAnnual variationvariation ofof transporttransport ofof KuroshioKuroshio currentcurrent

50 40 30

transport (Sv) 20 10 1975 1980 1985 1990 1995 2000 2005

Time series of the Kuroshio transport (Sv) along 137oE referenced to 1250m depth. Thick green line indicates its 2 years running mean value.

TimeTime seriesseries ofof thethe depthdepth ofof mixingmixing layerlayer onon OO--lineline

140 Inshore Kuroshio 34N 120 100 80 60 40 20 0 2002 2003 2004 2005 2006 2007 2008 2009 250 Offshore Kuroshio 30N

200

Mixing Layer Depth150 (m)

100

0 2002 2003 2004 2005 2006 2007 2008 2009 Seasonal variation is clearly observed (deep mixing layer → during winter)

TimeTime seriesseries ofof nutrientnutrient conditioncondition onon OO--lineline

（（NONO2+NO +NO3; ;μμmol/l)mol/l) Large meander period

According to deep mixing layer during water high nutrient concentration has been observed during winter. Time series of biomass of microzooplankton on O-line (mgC/m2) Dinoflagelｌates 34°N 30°N 3.2 1.2 0 1.0 0 1.6 5.6 0.8 0.8 0.8 0.8 1.6 -50 -50 0.2 0.4 0.4 0.4 -100 0.2 naked37987 Cilliates3835238717390823944739812 37987 38352 38717 39082 39447 39812 2.4 6.0 3.0 0 0 1.0 0.8 0.8 1.0 2.0 2.0 1.6 0.8 2.0 1.0 4.0 -50 0.4 1.0 2.0 3.0 1.0 -50 1.0 0.4 0.4 -100

37987 38352 38717 39082 39447 39812 379873835238717390823944739812 Depth (m) Depth Tintinnids 0 0.32 0.1 0.1 0.1 0.1 0.1 0 0.16 0.24 0.1 0.16 0.16 -50 0.2 0.08 0.08 -50 0.08 0.4 -100 0.6

37987 38352 38717 39082 39447 39812 Nauplius37987 larvae3835238717390823944739812 2.8 2.83.2 2.8 0 0.8 1.0 0 2.0 0.8 0.4 0.4 1.6 2.4 -50 0.4 0.4 0.4 2.0 0.4 0.2 -50 -100 0.2 0.2 2004 2005 2006 2007 2008 2009 2004 2005 2006 2007 2008 2009 37987 38352 38717 39082 39447 39812 379873835238717390823944739812 Year Clear annual trends or events were not observed from this dataset. Seasonal variation has been observed. (high biomass during spring) Good timing for feeding of early hatched larval fish (←Spawning peak is winter) Time series of Chla concentration at the station in Tosa bay（mg/m3）

Peak season become earlier recently?

3 Time series of small copepod (body width<0.1mm) biomass at the station in Tosa bay（mm3/m3)

Peak season become earlier recently? Time series of large copepod (body width>0.3mm) biomass at the station in Tosa bay（mm3/m3)

Before 2004, the high biomass peak had been observed from late winter to spring.

After 2004, spring peak was damped and biomass become relatively higher after summer.

Seasonal variation has become unclear during recent years. LongLong--termterm variationvariation ofof transparenciestransparencies ofof SardineSardine spawningspawning areaarea inin relationrelation toto climateclimate changechange region region air temperature Kuroshio Kuroshio precipitation radial period radial period Anomalies of transparencies in the the in transparencies Anomalies of Anomalies of transparencies in the the in transparencies Anomalies of wind stress wind stress

アメダス（高知） Climate regime shifshiftt seems to be related to the transparencies (≒biomass of primary producer） BenchBench--toptop VideoVideo PlanktonPlankton SamplerSampler (B(B--VPR)VPR)

For ecosystem change analysis, plankton species composition are needed. But microscopic analysis of formalin preserved samples costs lots of time and effort. →Quick and automatic analysis are needed.

B-VPR →analysis on abundance and size composition of copepods Resolution: 0.01 mm/pixel （Prosome length>0.4mm） a) 正面 Ability: 15-30 min / bottle

Flow cell and Video camera

Copepod ccapturedaptured by Video camera AuAutomatictomatic measurementmeasurement of body size Distribution of sampling stations for B-VPR analysis Area3 4 5

Zooplankton samples has been accumulated by the research on the distribution and abundances of egg and larval fish has been conducted by fisheries agency since 1950 around Japan. From this collection, 1300 samples (collected in 1964-2008) were used by B-VPR analysis. Time series of copepod biomass using B-VPR Anomaly West East

Large copepod

Small copepod Biomass of small copepod has been low since ’80s, while that of large copepod becomes high recently (especially at the western area; area3) Long-term variation of copepod species composition in relation to climate change and path of Kuroshio (Microscopic analysis) →Kuriyama et al. (W6) high Abundance high low Muroto Diversity low high Ashizuri

Community Small Mid Size P.parvus Large Kuroshio Small regime shift 19 300 SST

18 SST ( 200 17 ˚ C) 16 100 AshizuriMuroto and Kuroshio (m) axis

Distance between shoreline between Distance 15 0 14 1970 1980 1990 2000 2010 During the period of high abundance of sardine (before 1990), copepod biomass were high, and species diversity of copepods were low and small species (e.g. P parvus) were abundant. Microscopic analysis supported the result of B-VPR. ConclusionsConclusions C ont •• InterdisciplinaryInterdisciplinaryne inu monitoringmonitoring (O(O--line)hasline)has beenbeen conductedconducted atat ce o sKuroshioKuroshiou ssa currentcurrentus areaarea forfor moremore thanthan 1010 years.years. rvi va ry long •• Recently,Recently,l peakpeakfo seasonseason ofof copepodcopepod bloombloom hashas tendedtended toto a r -te becomebecome earlier,earlier,nd a naandand seasonalseasonalrm variationvariation ofof largelarge copepodcopepod p biomassbiomass hashas becomebecomero ly unclear.unclear.mo d sis ni •• TheThe timingtiming ofof changechangeuc ofofo ecoecosystemsystemt maymay bebe relatedrelated toto thethe ti f ori climateclimate changechange andand theothen changechangeclim ofofng meandermeander patternpattern ofof of ate o KuroshioKuroshio.. f f ish c ec •• LongLong--termterm variationvariation ofof ecosystemecosystem (e.g.(e.g.hang speciesspeciesosyste e compositioncomposition ofof copepods)copepods) inin relationrelation toto climateclimate e m changechange (regime(regime shift)shift) hashas beenbeen observedobserved usingusing newlynewlyffe designeddesignedis ct BenchBench--toptop VideoVideo PlanktonPlankton RecorderRecorder systemsystem usingusingon zooplanktonzooplankton samplessamples accumulaaccumulatedted aroundaround JapanJapan forfor moremore thanthan 50years.50years.